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Severe Tick-Borne Infections and Their Mimics in the Critical Care Unit
Published in Cheston B. Cunha, Burke A. Cunha, Infectious Diseases and Antimicrobial Stewardship in Critical Care Medicine, 2020
Praveen Sudhindra, Gary P. Wormser
Ehrlichia chaffeensis, a gram-negative intracellular bacterium, is the etiologic agent of HME. Infection occurs from the bite of an infected lone star tick (Amblyomma americanum). The highest incidence is in South Central and southeastern United States; however, the disease can potentially occur in any state in which this tick species is endemic [3,14].
Food allergens
Published in Richard F. Lockey, Dennis K. Ledford, Allergens and Allergen Immunotherapy, 2020
Several studies report evidence that tick bites may be responsible for the development of α-gal specific IgE. In the United States, the Amblyomma americanum, or lone star tick, has been implicated, whereas in France and Australia, the Ixodes ricinus and Ixodes holocyclus, respectively, are thought to be the culprit species [75]. Case reports of tick bites followed by subsequent reactions to beef, the presence of α-gal IgE, and the regional distribution of the responsible tick has provided convincing, although circumstantial, evidence that tick bites may trigger the production of α-gal IgE, the subsequent red meat allergy syndrome and reactions to cetuximab.
Rocky Mountain Spotted Fever and Typhus Fever
Published in James H. S. Gear, CRC Handbook of Viral and Rickettsial Hemorrhagic Fevers, 2019
Dermacentor ander soni (wood tick) and Dermacentor variabilis (dog tick) are the principal vectors in the western and eastern U.S., respectively. Other ticks of importance are Amblyomma americanum (lone star tick) in Texas and Oklahoma, Rhipicephalus sanguineus (brown dog tick) in Mexico and the U.S. (this tick is reservoir and vector of R. conorii infections), and Amblyomma cajennense in Brazil and Colombia.
Alpha-gal syndrome: challenges to understanding sensitization and clinical reactions to alpha-gal
Published in Expert Review of Molecular Diagnostics, 2020
José de la Fuente, Alejandro Cabezas-Cruz, Iván Pacheco
Among the co-factors associated to the AGS, several evidence show that exposure to tick bites is an essential risk factor for the development of this syndrome [6]: (i) tick bites elicit an increase in the levels of IgE to α-Gal of 20-fold or greater [2], (ii) most AGS patients have a history of tick bites [26,34,38], (iii) AGS patients have antibodies reactive to tick antigens [2], and (iv) a strong positive correlation between anti-α-Gal IgE and anti-tick IgE levels was reported [2,3]. However, some patients that develop strong allergic reactions to tick bites and have high levels of IgE to α-Gal are mammalian meat tolerant [9]. This finding suggests that mammalian meat allergy is a special type of allergy within a wide spectrum of allergies related to tick bites. AGS has been associated with several tick species including Amblyomma americanum (USA), Amblyomma sculptum (Brazil), Amblyomma testudinarium, and Haemaphysalis longicornis (Japan), Ixodes holocyclus (Australia) and the principal vector of Lyme disease in Europe, Ixodes ricinus [8,39]. Surprisingly, Ixodes scapularis, the main vector of Lyme disease in the USA, which produces α-Gal [40,41] and is closely related to I. ricinus, is almost certainly not a major cause of AGS in the USA [6].
Diagnosis & management of alpha-gal syndrome: lessons from 2,500 patients
Published in Expert Review of Clinical Immunology, 2020
Following identification of AGS, patients with the same allergy in Australia, Europe, Scandinavia, Japan, and South Africa have been reported [6]. Owing to the geographical range and analysis of tick salivary factors, the lone star tick (Amblyomma americanum) appears to be the primary cause of AGS in the U.S.; however, no case–control study has confirmed this link. An association between AGS and tick bites has been reported throughout the world, despite the differences in tick species and populations [6,8]. Blood levels of alpha-gal IgE often decrease in patients who avoid recurrent tick bites but the rate of decline varies from patient to patient [7]. The titer of alpha-gal specific IgE does not predict reaction severity; rather dose (amount consumed) and presence of co-factors (alcohol, activity) affect the delay before reaction and resulting clinical manifestations [4]. In keeping with other food allergies, clinical experience suggests that the presence of co-factors appears to lower the eliciting dose required for reactivity but this requires further study in AGS [9]. Specific to AGS, recent tick bites appear to make patients more sensitive to prior tolerated exposures or even lower threshold for reactivity. Table 1 is a summary of clinical points accumulated over the last decade caring for patients with AGS.
Tick transmission of toxoplasmosis
Published in Expert Review of Anti-infective Therapy, 2019
Although some studies were not successful in isolating T. gondii from ticks collected in natural habitats or in experimental transmission [43,59–62]., the differences might be explained with a better understanding of the ecology of ticks and their association with hosts in the different environments, including changes in tick abundance according to climatic conditions, host factors, socio-demographic factors, and agricultural and wildlife management [63]. More information is needed on how T. gondii survives in natural settings. For elucidation of some of the other questions concerning the possible transmission of T. gondii by ticks, further studies are needed. It is unclear which stage(s) of life cycle of the tick might permit the transmission of T. gondii and how the life cycle of the parasite is expressed in the tick body. Given the recently documented occurrence of Haemaphysalis longicornis in the US, and the ability of T. gondii to survive in this tick species, further evaluation of the potential role of Haemaphysalis longicornis in the transmission of this disease agent among animal reservoirs, and possibly to humans, is warranted. Another area needing study is the determination of any correlation to Amblyomma americanum (Lonestar tick), which is prevalent in the South and Mid-Atlantic Regions – corresponding to the higher geographic location of toxoplasmosis in the US. Woke et al. [19] found that Amblyomma americanum appeared to maintain T. gondii for extended periods of time after infection.